hydrodynamic analysis of multi body platform
Moderators: Bonnie.Jonkman, Jason.Jonkman

 Posts: 3
 Joined: Mon Sep 30, 2013 12:03 pm
 Organization: amirkabir university of technology
 Location: Iran
hydrodynamic analysis of multi body platform
dear jonkman
I'm interested in combined wave energy convertor and floating wind turbine systems. I don't have any access to WAMIT so I will use ANSYS AQWA for modeling and frequency domain analysis of this multi body system. is it possible to get result for this multi body system from Hydrodyn? how can I use Hydrodyne for this purpose ?
thanks a lot
best regards
I'm interested in combined wave energy convertor and floating wind turbine systems. I don't have any access to WAMIT so I will use ANSYS AQWA for modeling and frequency domain analysis of this multi body system. is it possible to get result for this multi body system from Hydrodyn? how can I use Hydrodyne for this purpose ?
thanks a lot
best regards

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Mehdi,
I know some panel codes (e.g., WAMIT) can model wavebody interaction between multiple bodies such that there is a direct interaction of the hydrodynamic wave scattering and radiation loads between the bodies. However, FAST/HydroDyn have not been developed to support this feature yet. Including this feature would take a bit of modification to HydroDyn and the addition of new structural degrees of freedom.
Best regards,
I know some panel codes (e.g., WAMIT) can model wavebody interaction between multiple bodies such that there is a direct interaction of the hydrodynamic wave scattering and radiation loads between the bodies. However, FAST/HydroDyn have not been developed to support this feature yet. Including this feature would take a bit of modification to HydroDyn and the addition of new structural degrees of freedom.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 3
 Joined: Mon Sep 30, 2013 12:03 pm
 Organization: amirkabir university of technology
 Location: Iran
Re: hydrodynamic analysis of multi body platform
Dear junkman
Thanks a lot for your kindly replying. as I understood you mean I should modify Hydrodyn source code.
as I don't have much time, is it possible for me to modify Hydrodyn ??? can you help me to overcome this project?
Thanks
Best Regards
Thanks a lot for your kindly replying. as I understood you mean I should modify Hydrodyn source code.
as I don't have much time, is it possible for me to modify Hydrodyn ??? can you help me to overcome this project?
Thanks
Best Regards

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Mehdi,
As I said, you would need to modify both HydroDyn and the structural model to include the hydrodynamic loads and structural DOFs of the additional floating bodies. I suspect this is quite a bit of work. FAST is open source, so, you are certainly free to do it, but NREL does not have sufficient resources to offer much guidance.
Best regards,
As I said, you would need to modify both HydroDyn and the structural model to include the hydrodynamic loads and structural DOFs of the additional floating bodies. I suspect this is quite a bit of work. FAST is open source, so, you are certainly free to do it, but NREL does not have sufficient resources to offer much guidance.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
Hi Jason,
Apologies for posting on an old thread but thought this was relevant. I am simulating a catamaran type floating platform to support a 5MW NREL reference wind turbine. I am observing an instability in sway which in turn creates an instability in roll and yaw modes. My model is a simplified catamaran with two hulls spaced apart with a plate on top that supports the turbine in the middle. Because the plate sits on top of the two hulls and thus out of water, does hydrodyn account for this connection? Is this why I am seeing an instability because of multibody interaction and OpenFASTs incapability to model multibody structures? When I disable Sway DOF the model completes furthermore.
Kind regards,
Josh
Apologies for posting on an old thread but thought this was relevant. I am simulating a catamaran type floating platform to support a 5MW NREL reference wind turbine. I am observing an instability in sway which in turn creates an instability in roll and yaw modes. My model is a simplified catamaran with two hulls spaced apart with a plate on top that supports the turbine in the middle. Because the plate sits on top of the two hulls and thus out of water, does hydrodyn account for this connection? Is this why I am seeing an instability because of multibody interaction and OpenFASTs incapability to model multibody structures? When I disable Sway DOF the model completes furthermore.
Kind regards,
Josh

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Josh,
NREL recently introduced the capability in OpenFAST to model floating substructures as flexible bodies with multiple potentialflow (WAMIT) bodies, but I suspect you are not using this capability yet (this functionality was introduced in the following pull request, which has been merged into the dev branch of OpenFAST, but is not yet in main: https://github.com/OpenFAST/openfast/pull/537).
Assuming you are not using this new capability, the floating substructure is modeled as a single sixdegree of freedom rigid body, even if the WAMIT solution or striptheory members in HydroDyn have two distinct pontoons that are physically connected by a plate above the water.
I don't think I can guess why your model is going unstable without knowing more about your model set up.
Best regards,
NREL recently introduced the capability in OpenFAST to model floating substructures as flexible bodies with multiple potentialflow (WAMIT) bodies, but I suspect you are not using this capability yet (this functionality was introduced in the following pull request, which has been merged into the dev branch of OpenFAST, but is not yet in main: https://github.com/OpenFAST/openfast/pull/537).
Assuming you are not using this new capability, the floating substructure is modeled as a single sixdegree of freedom rigid body, even if the WAMIT solution or striptheory members in HydroDyn have two distinct pontoons that are physically connected by a plate above the water.
I don't think I can guess why your model is going unstable without knowing more about your model set up.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
Dear Jason,
Thank you for point out this capability, I was not aware of this. In this situation though I am simulating the platform as a single rigid body.
If a multibody floating substructure was modelled as a single rigid body that should not make a simulation unstable, only less accurate as hydrodynamic interaction between the two bodies are not accounted for meaning there most likely is an error in my model?
My own model is a Catamarantype FOWT, 70m L x 45m W, each demi hull is 10 x 10 x 70. As a starting point I used similar dimensions to the ITI Energy Barge. Therefore, my model has the similar draft, freeboard, volume and mass and mooring system (except this has been adapted as my platform is slightly longer, I made sure similar initial tensions were obtained). The wind turbine itself is identical and has the same tower base height and I have not altered these input files i.e. AeroDyn and ServoDyn. I can send some results over and my OpenFAST model if required, what would be the best way to do this?
Kind regards,
Thank you for point out this capability, I was not aware of this. In this situation though I am simulating the platform as a single rigid body.
If a multibody floating substructure was modelled as a single rigid body that should not make a simulation unstable, only less accurate as hydrodynamic interaction between the two bodies are not accounted for meaning there most likely is an error in my model?
My own model is a Catamarantype FOWT, 70m L x 45m W, each demi hull is 10 x 10 x 70. As a starting point I used similar dimensions to the ITI Energy Barge. Therefore, my model has the similar draft, freeboard, volume and mass and mooring system (except this has been adapted as my platform is slightly longer, I made sure similar initial tensions were obtained). The wind turbine itself is identical and has the same tower base height and I have not altered these input files i.e. AeroDyn and ServoDyn. I can send some results over and my OpenFAST model if required, what would be the best way to do this?
Kind regards,

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Josh,
You haven't really described enough about your model set up or obtained results for me to comment, but it sounds like your model is not behaving as you expect. Adding floater flexibility would only complicate the model, not help with instability.
Can you clarify what you mean by "instability"?
I would first suggest simplifying to debug. Does your model maintain hydrostatic equilibrium if you disable aerodynamics (CompAero = 0) and use still water (WaveMod = 0)? If so, what feature, when enabled, results in the unstable response you are describing?
Best regards,
You haven't really described enough about your model set up or obtained results for me to comment, but it sounds like your model is not behaving as you expect. Adding floater flexibility would only complicate the model, not help with instability.
Can you clarify what you mean by "instability"?
I would first suggest simplifying to debug. Does your model maintain hydrostatic equilibrium if you disable aerodynamics (CompAero = 0) and use still water (WaveMod = 0)? If so, what feature, when enabled, results in the unstable response you are describing?
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
Dear Jason,
My apologies for lack of thoroughness. I have attempted to debug myself. I initially ran a simulation T = 4000s, a turbulent wind condition at rated wind speed with an irregular wave (Ts = 5.01s, Hs = 1.94m). I applied a rotor speed of 12.1 rpm as a initial condition.
After the transient effect period wears off, for sway and roll modes they begin to grow in amplitude exponentially. This was my first observation of the instability. So I then ran a regular wave case only with same period and wave height as the irregular wave and reset initial conditions. I have attached the rigid body modes of this simulation. I thought this was the error when introducing a wave climate, so to confirm this I ran a wind only condition too with WaveMod = 0, however the same instability occurs.
I have carried out a free decay analysis and run a simulation with the conditions you have suggest and the platform reached a steady state equilibrium for 4000s. It is only when I introduce a wind/wave climate that the instability occurs.
Kind regards,
Josh
Note this is correct roll response from regular wave case, as in the previous image was the sway response.
My apologies for lack of thoroughness. I have attempted to debug myself. I initially ran a simulation T = 4000s, a turbulent wind condition at rated wind speed with an irregular wave (Ts = 5.01s, Hs = 1.94m). I applied a rotor speed of 12.1 rpm as a initial condition.
After the transient effect period wears off, for sway and roll modes they begin to grow in amplitude exponentially. This was my first observation of the instability. So I then ran a regular wave case only with same period and wave height as the irregular wave and reset initial conditions. I have attached the rigid body modes of this simulation. I thought this was the error when introducing a wave climate, so to confirm this I ran a wind only condition too with WaveMod = 0, however the same instability occurs.
I have carried out a free decay analysis and run a simulation with the conditions you have suggest and the platform reached a steady state equilibrium for 4000s. It is only when I introduce a wind/wave climate that the instability occurs.
Kind regards,
Josh
Note this is correct roll response from regular wave case, as in the previous image was the sway response.
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 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
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Re: hydrodynamic analysis of multi body platform
Dear Josh,
OK, thanks for clarifying. I see the unstable behaviour, but is odd to me that it does not appear until about 3 hours into the simulation. Is there something (e.g., controller related) that changes at this point? It is not common to wrong simulations this long; what is your reason for doing so?
I gather from your post that the instability is winddriven. Can you confirm that you do not see any signs of instability for simulations without aerodynamics?
Best regards,
OK, thanks for clarifying. I see the unstable behaviour, but is odd to me that it does not appear until about 3 hours into the simulation. Is there something (e.g., controller related) that changes at this point? It is not common to wrong simulations this long; what is your reason for doing so?
I gather from your post that the instability is winddriven. Can you confirm that you do not see any signs of instability for simulations without aerodynamics?
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
Dear Jason,
I have solved the instability. However I am not sure of the reasoning. I have attached two HydroDyn input files. The first that caused the instability I removed all the data from the striptheory section such as axial coefficients, member coefficients so on and so forth. I presumed this would not affect my model (clearly I was wrong) as using potential theory to model the hydrodynamics. The second keeps the default values from the ITI Energy Barge. Do you have any idea as to why this would cause an instability?
NOTE: Instabilities occurred after 1300s not 13000s, it was an improper format in excel.
Kind regards,
Josh
I have solved the instability. However I am not sure of the reasoning. I have attached two HydroDyn input files. The first that caused the instability I removed all the data from the striptheory section such as axial coefficients, member coefficients so on and so forth. I presumed this would not affect my model (clearly I was wrong) as using potential theory to model the hydrodynamics. The second keeps the default values from the ITI Energy Barge. Do you have any idea as to why this would cause an instability?
NOTE: Instabilities occurred after 1300s not 13000s, it was an improper format in excel.
Kind regards,
Josh
Last edited by Joshua.Cutler on Tue Apr 06, 2021 3:33 pm, edited 1 time in total.

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
 HydroDyn v2.03.* Input File 
NREL 5.0 MW offshore baseline floating platform HydroDyn input properties for the ITI Barge with 4m draft.
False Echo  Echo the input file data (flag)
 ENVIRONMENTAL CONDITIONS 
1025 WtrDens  Water density (kg/m^3)
150 WtrDpth  Water depth (meters)
0 MSL2SWL  Offset between stillwater level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
 WAVES 
0 WaveMod  Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with userspecified phase, 2: JONSWAP/PiersonMoskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: userdefined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated waveelevation time series, 6: Externally generated full wavekinematics time series [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod  Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
4000 WaveTMax  Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT  Time step for incident wave calculations (sec) [unused when WaveMod=0; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
1.94 WaveHs  Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
5.01 WaveTp  Peakspectral period of incident waves (sec) [used only when WaveMod=1 or 2]
"1.0" WavePkShp  Peakshape parameter of incident wave spectrum () or DEFAULT (string) [used only when WaveMod=2; use 1.0 for PiersonMoskowitz]
0 WvLowCOff  Low cutoff frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
500 WvHiCOff  High cutoff frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
0 WaveDir  Incident wave propagation heading direction (degrees) [unused when WaveMod=0 or 6]
0 WaveDirMod  Directional spreading function {0: none, 1: COS2S} () [only used when WaveMod=2,3, or 4]
1 WaveDirSpread  Wave direction spreading coefficient ( > 0 ) () [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir  Number of wave directions () [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange  Range of wave directions (full range: WaveDir +/ 1/2*WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1)  First random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
1011121314 WaveSeed(2)  Second random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp  Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
"" WvKinFile  Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5 or 6]
1 NWaveElev  Number of points where the incident wave elevations can be computed () [maximum of 9 output locations]
0 WaveElevxi  List of xicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi  List of yicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
 2NDORDER WAVES  [unused with WaveMod=0 or 6]
False WvDiffQTF  Full differencefrequency 2ndorder wave kinematics (flag)
False WvSumQTF  Full summationfrequency 2ndorder wave kinematics (flag)
0 WvLowCOffD  Low frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
3.5 WvHiCOffD  High frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
0.1 WvLowCOffS  Low frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
3.5 WvHiCOffS  High frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
 CURRENT  [unused with WaveMod=6]
0 CurrMod  Current profile model {0: none=no current, 1: standard, 2: userdefined from routine UserCurrent} (switch)
0 CurrSSV0  Subsurface current velocity at still water level (m/s) [used only when CurrMod=1]
"DEFAULT" CurrSSDir  Subsurface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef  Nearsurface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0  Nearsurface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir  Nearsurface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV  Depthindependent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir  Depthindependent current heading direction (degrees) [used only when CurrMod=1]
 FLOATING PLATFORM  [unused with WaveMod=6]
1 PotMod  Potentialflow model {0: none=no potential flow, 1: frequencytotimedomain transforms based on WAMIT output, 2: fluidimpulse theory (FIT)} (switch)
"../5MW_Baseline/HydroData/WAMITFILES" PotFile  Root name of potentialflow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequencydependent hydrodynamic added mass matrix and damping matrix (.1), and frequency and directiondependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLYSIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO AND INFINITEFREQUENCY LIMITS!]
1 WAMITULEN  Characteristic body length scale used to redimensionalize WAMIT output (meters) [only used when PotMod=1]
5500.5874 PtfmVol0  Displaced volume of water when the platform is in its undisplaced position (m^3) [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt  The xt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 PtfmCOByt  The yt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
1 ExctnMod  Wave Excitation model {0: None, 1: DFT, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ssexctn INPUT FILE]
1 RdtnMod  Radiation memoryeffect model {0: no memoryeffect calculation, 1: convolution, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ss INPUT FILE]
60 RdtnTMax  Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEARZERO FOR THE GIVEN PLATFORM!]
"DEFAULT" RdtnDT  Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod=1; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
 2NDORDER FLOATING PLATFORM FORCES  [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift  Meandrift 2ndorder forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 NewmanApp  Mean and slowdrift 2ndorder forces computed with Newman's approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero. Used only when WaveDirMod=0]
0 DiffQTF  Full differencefrequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 SumQTF  Full summation frequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
 FLOATING PLATFORM FORCE FLAGS  [unused with WaveMod=6]
True PtfmSgF  Platform horizontal surge translation force (flag) or DEFAULT
True PtfmSwF  Platform horizontal sway translation force (flag) or DEFAULT
True PtfmHvF  Platform vertical heave translation force (flag) or DEFAULT
True PtfmRF  Platform roll tilt rotation force (flag) or DEFAULT
True PtfmPF  Platform pitch tilt rotation force (flag) or DEFAULT
True PtfmYF  Platform yaw rotation force (flag) or DEFAULT
 PLATFORM ADDITIONAL STIFFNESS AND DAMPING 
0 0 0 0 0 0 AddF0  Additional preload (N, Nm)
0 0 0 0 0 0 AddCLin  Additional linear stiffness (N/m, N/rad, Nm/m, Nm/rad)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBLin  Additional linear damping(N/(m/s), N/(rad/s), Nm/(m/s), Nm/(rad/s))
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBQuad  Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, Nm(m/s)^2, Nm/(rad/s)^2)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
 AXIAL COEFFICIENTS 
0 NAxCoef  Number of axial coefficients ()
AxCoefID AxCd AxCa AxCp
() () () ()
 MEMBER JOINTS 
0 NJoints  Number of joints () [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
() (m) (m) (m) () (switch)
 MEMBER CROSSSECTION PROPERTIES 
0 NPropSets  Number of member property sets ()
PropSetID PropD PropThck
() (m) (m)
 SIMPLE HYDRODYNAMIC COEFFICIENTS (model 1) 
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG
() () () () () () () () () ()
1.00 1.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00
 DEPTHBASED HYDRODYNAMIC COEFFICIENTS (model 2) 
0 NCoefDpth  Number of depthdependent coefficients ()
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG
(m) () () () () () () () () () ()
 MEMBERBASED HYDRODYNAMIC COEFFICIENTS (model 3) 
0 NCoefMembers  Number of memberbased coefficients ()
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2
() () () () () () () () () () () () () () () () () () () () ()
 MEMBERS 
0 NMembers  Number of members ()
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MDivSize MCoefMod PropPot [MCoefMod=1: use simple coeff table, 2: use depthbased coeff table, 3: use memberbased coeff table] [ PropPot/=0 if member is modeled with potentialflow theory]
() () () () () (m) (switch) (flag)
 FILLED MEMBERS 
0 NFillGroups  Number of filled member groups () [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
() () (m) (kg/m^3)
 MARINE GROWTH 
0 NMGDepths  Number of marinegrowth depths specified ()
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
 MEMBER OUTPUT LIST 
0 NMOutputs  Number of member outputs () [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
() () ()
 JOINT OUTPUT LIST 
0 NJOutputs  Number of joint outputs [Must be < 10]
0 JOutLst  List of JointIDs which are to be output ()[unused if NJOutputs=0]
 OUTPUT 
True HDSum  Output a summary file [flag]
False OutAll  Output all userspecified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch  Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
"ES11.4e2" OutFmt  Output format for numerical results (quoted string) [not checked for validity!]
"A11" OutSFmt  Output format for header strings (quoted string) [not checked for validity!]
 OUTPUT CHANNELS 
"Wave1Elev"  Wave elevation at the platform reference point ( 0, 0)
END of output channels and end of file. (the word "END" must appear in the first 3 columns of this line)
 HydroDyn v2.03.* Input File 
NREL 5.0 MW offshore baseline floating platform HydroDyn input properties for the ITI Barge with 4m draft.
False Echo  Echo the input file data (flag)
 ENVIRONMENTAL CONDITIONS 
1025 WtrDens  Water density (kg/m^3)
150 WtrDpth  Water depth (meters)
0 MSL2SWL  Offset between stillwater level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
 WAVES 
1 WaveMod  Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with userspecified phase, 2: JONSWAP/PiersonMoskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: userdefined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated waveelevation time series, 6: Externally generated full wavekinematics time series [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod  Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
4000 WaveTMax  Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT  Time step for incident wave calculations (sec) [unused when WaveMod=0; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
1.94 WaveHs  Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
5.01 WaveTp  Peakspectral period of incident waves (sec) [used only when WaveMod=1 or 2]
"DEFAULT" WavePkShp  Peakshape parameter of incident wave spectrum () or DEFAULT (string) [used only when WaveMod=2; use 1.0 for PiersonMoskowitz]
0 WvLowCOff  Low cutoff frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
500 WvHiCOff  High cutoff frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
0 WaveDir  Incident wave propagation heading direction (degrees) [unused when WaveMod=0 or 6]
0 WaveDirMod  Directional spreading function {0: none, 1: COS2S} () [only used when WaveMod=2,3, or 4]
1 WaveDirSpread  Wave direction spreading coefficient ( > 0 ) () [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir  Number of wave directions () [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange  Range of wave directions (full range: WaveDir +/ 1/2*WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1)  First random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
1011121314 WaveSeed(2)  Second random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp  Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
"" WvKinFile  Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5 or 6]
1 NWaveElev  Number of points where the incident wave elevations can be computed () [maximum of 9 output locations]
0 WaveElevxi  List of xicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi  List of yicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
 2NDORDER WAVES  [unused with WaveMod=0 or 6]
False WvDiffQTF  Full differencefrequency 2ndorder wave kinematics (flag)
False WvSumQTF  Full summationfrequency 2ndorder wave kinematics (flag)
0 WvLowCOffD  Low frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
3.5 WvHiCOffD  High frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
0.1 WvLowCOffS  Low frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
3.5 WvHiCOffS  High frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
 CURRENT  [unused with WaveMod=6]
0 CurrMod  Current profile model {0: none=no current, 1: standard, 2: userdefined from routine UserCurrent} (switch)
0 CurrSSV0  Subsurface current velocity at still water level (m/s) [used only when CurrMod=1]
"DEFAULT" CurrSSDir  Subsurface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef  Nearsurface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0  Nearsurface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir  Nearsurface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV  Depthindependent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir  Depthindependent current heading direction (degrees) [used only when CurrMod=1]
 FLOATING PLATFORM  [unused with WaveMod=6]
1 PotMod  Potentialflow model {0: none=no potential flow, 1: frequencytotimedomain transforms based on WAMIT output, 2: fluidimpulse theory (FIT)} (switch)
"../5MW_Baseline/HydroData/WAMITFILES" PotFile  Root name of potentialflow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequencydependent hydrodynamic added mass matrix and damping matrix (.1), and frequency and directiondependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLYSIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO AND INFINITEFREQUENCY LIMITS!]
1 WAMITULEN  Characteristic body length scale used to redimensionalize WAMIT output (meters) [only used when PotMod=1]
5500.5874 PtfmVol0  Displaced volume of water when the platform is in its undisplaced position (m^3) [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt  The xt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 PtfmCOByt  The yt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 ExctnMod  Wave Excitation model {0: None, 1: DFT, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ssexctn INPUT FILE]
0 RdtnMod  Radiation memoryeffect model {0: no memoryeffect calculation, 1: convolution, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ss INPUT FILE]
60 RdtnTMax  Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEARZERO FOR THE GIVEN PLATFORM!]
"DEFAULT" RdtnDT  Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod=1; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
 2NDORDER FLOATING PLATFORM FORCES  [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift  Meandrift 2ndorder forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 NewmanApp  Mean and slowdrift 2ndorder forces computed with Newman's approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero. Used only when WaveDirMod=0]
0 DiffQTF  Full differencefrequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 SumQTF  Full summation frequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
 FLOATING PLATFORM FORCE FLAGS  [unused with WaveMod=6]
True PtfmSgF  Platform horizontal surge translation force (flag) or DEFAULT
True PtfmSwF  Platform horizontal sway translation force (flag) or DEFAULT
True PtfmHvF  Platform vertical heave translation force (flag) or DEFAULT
True PtfmRF  Platform roll tilt rotation force (flag) or DEFAULT
True PtfmPF  Platform pitch tilt rotation force (flag) or DEFAULT
True PtfmYF  Platform yaw rotation force (flag) or DEFAULT
 PLATFORM ADDITIONAL STIFFNESS AND DAMPING 
0 0 0 0 0 0 AddF0  Additional preload (N, Nm)
0 0 0 0 0 0 AddCLin  Additional linear stiffness (N/m, N/rad, Nm/m, Nm/rad)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBLin  Additional linear damping(N/(m/s), N/(rad/s), Nm/(m/s), Nm/(rad/s))
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBQuad  Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, Nm(m/s)^2, Nm/(rad/s)^2)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
 AXIAL COEFFICIENTS 
1 NAxCoef  Number of axial coefficients ()
AxCoefID AxCd AxCa AxCp
() () () ()
1 0.00 0.00 1.00
 MEMBER JOINTS 
2 NJoints  Number of joints () [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
() (m) (m) (m) () (switch)
1 0.00000 0.00000 4.00000 1 0
2 0.00000 0.00000 0.00000 1 0
 MEMBER CROSSSECTION PROPERTIES 
1 NPropSets  Number of member property sets ()
PropSetID PropD PropThck
() (m) (m)
1 45.13520 0.00010
 SIMPLE HYDRODYNAMIC COEFFICIENTS (model 1) 
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG
() () () () () () () () () ()
1.00 1.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00
 DEPTHBASED HYDRODYNAMIC COEFFICIENTS (model 2) 
0 NCoefDpth  Number of depthdependent coefficients ()
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG
(m) () () () () () () () () () ()
 MEMBERBASED HYDRODYNAMIC COEFFICIENTS (model 3) 
0 NCoefMembers  Number of memberbased coefficients ()
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2
() () () () () () () () () () () () () () () () () () () () ()
 MEMBERS 
1 NMembers  Number of members ()
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MDivSize MCoefMod PropPot [MCoefMod=1: use simple coeff table, 2: use depthbased coeff table, 3: use memberbased coeff table] [ PropPot/=0 if member is modeled with potentialflow theory]
() () () () () (m) (switch) (flag)
1 1 2 1 1 0.5000 1 TRUE
 FILLED MEMBERS 
0 NFillGroups  Number of filled member groups () [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
() () (m) (kg/m^3)
 MARINE GROWTH 
0 NMGDepths  Number of marinegrowth depths specified ()
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
 MEMBER OUTPUT LIST 
0 NMOutputs  Number of member outputs () [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
() () ()
 JOINT OUTPUT LIST 
0 NJOutputs  Number of joint outputs [Must be < 10]
0 JOutLst  List of JointIDs which are to be output ()[unused if NJOutputs=0]
 OUTPUT 
True HDSum  Output a summary file [flag]
False OutAll  Output all userspecified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch  Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
"ES11.4e2" OutFmt  Output format for numerical results (quoted string) [not checked for validity!]
"A11" OutSFmt  Output format for header strings (quoted string) [not checked for validity!]
 OUTPUT CHANNELS 
"Wave1Elev"  Wave elevation at the platform reference point ( 0, 0)
END of output channels and end of file. (the word "END" must appear in the first 3 columns of this line)
NREL 5.0 MW offshore baseline floating platform HydroDyn input properties for the ITI Barge with 4m draft.
False Echo  Echo the input file data (flag)
 ENVIRONMENTAL CONDITIONS 
1025 WtrDens  Water density (kg/m^3)
150 WtrDpth  Water depth (meters)
0 MSL2SWL  Offset between stillwater level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
 WAVES 
0 WaveMod  Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with userspecified phase, 2: JONSWAP/PiersonMoskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: userdefined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated waveelevation time series, 6: Externally generated full wavekinematics time series [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod  Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
4000 WaveTMax  Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT  Time step for incident wave calculations (sec) [unused when WaveMod=0; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
1.94 WaveHs  Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
5.01 WaveTp  Peakspectral period of incident waves (sec) [used only when WaveMod=1 or 2]
"1.0" WavePkShp  Peakshape parameter of incident wave spectrum () or DEFAULT (string) [used only when WaveMod=2; use 1.0 for PiersonMoskowitz]
0 WvLowCOff  Low cutoff frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
500 WvHiCOff  High cutoff frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
0 WaveDir  Incident wave propagation heading direction (degrees) [unused when WaveMod=0 or 6]
0 WaveDirMod  Directional spreading function {0: none, 1: COS2S} () [only used when WaveMod=2,3, or 4]
1 WaveDirSpread  Wave direction spreading coefficient ( > 0 ) () [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir  Number of wave directions () [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange  Range of wave directions (full range: WaveDir +/ 1/2*WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1)  First random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
1011121314 WaveSeed(2)  Second random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp  Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
"" WvKinFile  Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5 or 6]
1 NWaveElev  Number of points where the incident wave elevations can be computed () [maximum of 9 output locations]
0 WaveElevxi  List of xicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi  List of yicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
 2NDORDER WAVES  [unused with WaveMod=0 or 6]
False WvDiffQTF  Full differencefrequency 2ndorder wave kinematics (flag)
False WvSumQTF  Full summationfrequency 2ndorder wave kinematics (flag)
0 WvLowCOffD  Low frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
3.5 WvHiCOffD  High frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
0.1 WvLowCOffS  Low frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
3.5 WvHiCOffS  High frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
 CURRENT  [unused with WaveMod=6]
0 CurrMod  Current profile model {0: none=no current, 1: standard, 2: userdefined from routine UserCurrent} (switch)
0 CurrSSV0  Subsurface current velocity at still water level (m/s) [used only when CurrMod=1]
"DEFAULT" CurrSSDir  Subsurface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef  Nearsurface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0  Nearsurface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir  Nearsurface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV  Depthindependent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir  Depthindependent current heading direction (degrees) [used only when CurrMod=1]
 FLOATING PLATFORM  [unused with WaveMod=6]
1 PotMod  Potentialflow model {0: none=no potential flow, 1: frequencytotimedomain transforms based on WAMIT output, 2: fluidimpulse theory (FIT)} (switch)
"../5MW_Baseline/HydroData/WAMITFILES" PotFile  Root name of potentialflow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequencydependent hydrodynamic added mass matrix and damping matrix (.1), and frequency and directiondependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLYSIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO AND INFINITEFREQUENCY LIMITS!]
1 WAMITULEN  Characteristic body length scale used to redimensionalize WAMIT output (meters) [only used when PotMod=1]
5500.5874 PtfmVol0  Displaced volume of water when the platform is in its undisplaced position (m^3) [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt  The xt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 PtfmCOByt  The yt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
1 ExctnMod  Wave Excitation model {0: None, 1: DFT, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ssexctn INPUT FILE]
1 RdtnMod  Radiation memoryeffect model {0: no memoryeffect calculation, 1: convolution, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ss INPUT FILE]
60 RdtnTMax  Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEARZERO FOR THE GIVEN PLATFORM!]
"DEFAULT" RdtnDT  Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod=1; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
 2NDORDER FLOATING PLATFORM FORCES  [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift  Meandrift 2ndorder forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 NewmanApp  Mean and slowdrift 2ndorder forces computed with Newman's approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero. Used only when WaveDirMod=0]
0 DiffQTF  Full differencefrequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 SumQTF  Full summation frequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
 FLOATING PLATFORM FORCE FLAGS  [unused with WaveMod=6]
True PtfmSgF  Platform horizontal surge translation force (flag) or DEFAULT
True PtfmSwF  Platform horizontal sway translation force (flag) or DEFAULT
True PtfmHvF  Platform vertical heave translation force (flag) or DEFAULT
True PtfmRF  Platform roll tilt rotation force (flag) or DEFAULT
True PtfmPF  Platform pitch tilt rotation force (flag) or DEFAULT
True PtfmYF  Platform yaw rotation force (flag) or DEFAULT
 PLATFORM ADDITIONAL STIFFNESS AND DAMPING 
0 0 0 0 0 0 AddF0  Additional preload (N, Nm)
0 0 0 0 0 0 AddCLin  Additional linear stiffness (N/m, N/rad, Nm/m, Nm/rad)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBLin  Additional linear damping(N/(m/s), N/(rad/s), Nm/(m/s), Nm/(rad/s))
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBQuad  Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, Nm(m/s)^2, Nm/(rad/s)^2)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
 AXIAL COEFFICIENTS 
0 NAxCoef  Number of axial coefficients ()
AxCoefID AxCd AxCa AxCp
() () () ()
 MEMBER JOINTS 
0 NJoints  Number of joints () [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
() (m) (m) (m) () (switch)
 MEMBER CROSSSECTION PROPERTIES 
0 NPropSets  Number of member property sets ()
PropSetID PropD PropThck
() (m) (m)
 SIMPLE HYDRODYNAMIC COEFFICIENTS (model 1) 
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG
() () () () () () () () () ()
1.00 1.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00
 DEPTHBASED HYDRODYNAMIC COEFFICIENTS (model 2) 
0 NCoefDpth  Number of depthdependent coefficients ()
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG
(m) () () () () () () () () () ()
 MEMBERBASED HYDRODYNAMIC COEFFICIENTS (model 3) 
0 NCoefMembers  Number of memberbased coefficients ()
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2
() () () () () () () () () () () () () () () () () () () () ()
 MEMBERS 
0 NMembers  Number of members ()
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MDivSize MCoefMod PropPot [MCoefMod=1: use simple coeff table, 2: use depthbased coeff table, 3: use memberbased coeff table] [ PropPot/=0 if member is modeled with potentialflow theory]
() () () () () (m) (switch) (flag)
 FILLED MEMBERS 
0 NFillGroups  Number of filled member groups () [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
() () (m) (kg/m^3)
 MARINE GROWTH 
0 NMGDepths  Number of marinegrowth depths specified ()
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
 MEMBER OUTPUT LIST 
0 NMOutputs  Number of member outputs () [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
() () ()
 JOINT OUTPUT LIST 
0 NJOutputs  Number of joint outputs [Must be < 10]
0 JOutLst  List of JointIDs which are to be output ()[unused if NJOutputs=0]
 OUTPUT 
True HDSum  Output a summary file [flag]
False OutAll  Output all userspecified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch  Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
"ES11.4e2" OutFmt  Output format for numerical results (quoted string) [not checked for validity!]
"A11" OutSFmt  Output format for header strings (quoted string) [not checked for validity!]
 OUTPUT CHANNELS 
"Wave1Elev"  Wave elevation at the platform reference point ( 0, 0)
END of output channels and end of file. (the word "END" must appear in the first 3 columns of this line)
 HydroDyn v2.03.* Input File 
NREL 5.0 MW offshore baseline floating platform HydroDyn input properties for the ITI Barge with 4m draft.
False Echo  Echo the input file data (flag)
 ENVIRONMENTAL CONDITIONS 
1025 WtrDens  Water density (kg/m^3)
150 WtrDpth  Water depth (meters)
0 MSL2SWL  Offset between stillwater level and mean sea level (meters) [positive upward; unused when WaveMod = 6; must be zero if PotMod=1 or 2]
 WAVES 
1 WaveMod  Incident wave kinematics model {0: none=still water, 1: regular (periodic), 1P#: regular with userspecified phase, 2: JONSWAP/PiersonMoskowitz spectrum (irregular), 3: White noise spectrum (irregular), 4: userdefined spectrum from routine UserWaveSpctrm (irregular), 5: Externally generated waveelevation time series, 6: Externally generated full wavekinematics time series [option 6 is invalid for PotMod/=0]} (switch)
0 WaveStMod  Model for stretching incident wave kinematics to instantaneous free surface {0: none=no stretching, 1: vertical stretching, 2: extrapolation stretching, 3: Wheeler stretching} (switch) [unused when WaveMod=0 or when PotMod/=0]
4000 WaveTMax  Analysis time for incident wave calculations (sec) [unused when WaveMod=0; determines WaveDOmega=2Pi/WaveTMax in the IFFT]
0.25 WaveDT  Time step for incident wave calculations (sec) [unused when WaveMod=0; 0.1<=WaveDT<=1.0 recommended; determines WaveOmegaMax=Pi/WaveDT in the IFFT]
1.94 WaveHs  Significant wave height of incident waves (meters) [used only when WaveMod=1, 2, or 3]
5.01 WaveTp  Peakspectral period of incident waves (sec) [used only when WaveMod=1 or 2]
"DEFAULT" WavePkShp  Peakshape parameter of incident wave spectrum () or DEFAULT (string) [used only when WaveMod=2; use 1.0 for PiersonMoskowitz]
0 WvLowCOff  Low cutoff frequency or lower frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
500 WvHiCOff  High cutoff frequency or upper frequency limit of the wave spectrum beyond which the wave spectrum is zeroed (rad/s) [unused when WaveMod=0, 1, or 6]
0 WaveDir  Incident wave propagation heading direction (degrees) [unused when WaveMod=0 or 6]
0 WaveDirMod  Directional spreading function {0: none, 1: COS2S} () [only used when WaveMod=2,3, or 4]
1 WaveDirSpread  Wave direction spreading coefficient ( > 0 ) () [only used when WaveMod=2,3, or 4 and WaveDirMod=1]
1 WaveNDir  Number of wave directions () [only used when WaveMod=2,3, or 4 and WaveDirMod=1; odd number only]
90 WaveDirRange  Range of wave directions (full range: WaveDir +/ 1/2*WaveDirRange) (degrees) [only used when WaveMod=2,3,or 4 and WaveDirMod=1]
123456789 WaveSeed(1)  First random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
1011121314 WaveSeed(2)  Second random seed of incident waves [2147483648 to 2147483647] () [unused when WaveMod=0, 5, or 6]
TRUE WaveNDAmp  Flag for normally distributed amplitudes (flag) [only used when WaveMod=2, 3, or 4]
"" WvKinFile  Root name of externally generated wave data file(s) (quoted string) [used only when WaveMod=5 or 6]
1 NWaveElev  Number of points where the incident wave elevations can be computed () [maximum of 9 output locations]
0 WaveElevxi  List of xicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
0 WaveElevyi  List of yicoordinates for points where the incident wave elevations can be output (meters) [NWaveElev points, separated by commas or white space; usused if NWaveElev = 0]
 2NDORDER WAVES  [unused with WaveMod=0 or 6]
False WvDiffQTF  Full differencefrequency 2ndorder wave kinematics (flag)
False WvSumQTF  Full summationfrequency 2ndorder wave kinematics (flag)
0 WvLowCOffD  Low frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
3.5 WvHiCOffD  High frequency cutoff used in the differencefrequencies (rad/s) [Only used with a differencefrequency method]
0.1 WvLowCOffS  Low frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
3.5 WvHiCOffS  High frequency cutoff used in the summationfrequencies (rad/s) [Only used with a summationfrequency method]
 CURRENT  [unused with WaveMod=6]
0 CurrMod  Current profile model {0: none=no current, 1: standard, 2: userdefined from routine UserCurrent} (switch)
0 CurrSSV0  Subsurface current velocity at still water level (m/s) [used only when CurrMod=1]
"DEFAULT" CurrSSDir  Subsurface current heading direction (degrees) or DEFAULT (string) [used only when CurrMod=1]
20 CurrNSRef  Nearsurface current reference depth (meters) [used only when CurrMod=1]
0 CurrNSV0  Nearsurface current velocity at still water level (m/s) [used only when CurrMod=1]
0 CurrNSDir  Nearsurface current heading direction (degrees) [used only when CurrMod=1]
0 CurrDIV  Depthindependent current velocity (m/s) [used only when CurrMod=1]
0 CurrDIDir  Depthindependent current heading direction (degrees) [used only when CurrMod=1]
 FLOATING PLATFORM  [unused with WaveMod=6]
1 PotMod  Potentialflow model {0: none=no potential flow, 1: frequencytotimedomain transforms based on WAMIT output, 2: fluidimpulse theory (FIT)} (switch)
"../5MW_Baseline/HydroData/WAMITFILES" PotFile  Root name of potentialflow model data; WAMIT output files containing the linear, nondimensionalized, hydrostatic restoring matrix (.hst), frequencydependent hydrodynamic added mass matrix and damping matrix (.1), and frequency and directiondependent wave excitation force vector per unit wave amplitude (.3) (quoted string) [MAKE SURE THE FREQUENCIES INHERENT IN THESE WAMIT FILES SPAN THE PHYSICALLYSIGNIFICANT RANGE OF FREQUENCIES FOR THE GIVEN PLATFORM; THEY MUST CONTAIN THE ZERO AND INFINITEFREQUENCY LIMITS!]
1 WAMITULEN  Characteristic body length scale used to redimensionalize WAMIT output (meters) [only used when PotMod=1]
5500.5874 PtfmVol0  Displaced volume of water when the platform is in its undisplaced position (m^3) [only used when PotMod=1; USE THE SAME VALUE COMPUTED BY WAMIT AS OUTPUT IN THE .OUT FILE!]
0 PtfmCOBxt  The xt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 PtfmCOByt  The yt offset of the center of buoyancy (COB) from the platform reference point (meters) [only used when PotMod=1]
0 ExctnMod  Wave Excitation model {0: None, 1: DFT, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ssexctn INPUT FILE]
0 RdtnMod  Radiation memoryeffect model {0: no memoryeffect calculation, 1: convolution, 2: statespace} (switch) [only used when PotMod=1; STATESPACE REQUIRES *.ss INPUT FILE]
60 RdtnTMax  Analysis time for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod>0; determines RdtnDOmega=Pi/RdtnTMax in the cosine transform; MAKE SURE THIS IS LONG ENOUGH FOR THE RADIATION IMPULSE RESPONSE FUNCTIONS TO DECAY TO NEARZERO FOR THE GIVEN PLATFORM!]
"DEFAULT" RdtnDT  Time step for wave radiation kernel calculations (sec) [only used when PotMod=1 and RdtnMod=1; DT<=RdtnDT<=0.1 recommended; determines RdtnOmegaMax=Pi/RdtnDT in the cosine transform]
 2NDORDER FLOATING PLATFORM FORCES  [unused with WaveMod=0 or 6, or PotMod=0 or 2]
0 MnDrift  Meandrift 2ndorder forces computed {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 NewmanApp  Mean and slowdrift 2ndorder forces computed with Newman's approximation {0: None; [7, 8, 9, 10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero. Used only when WaveDirMod=0]
0 DiffQTF  Full differencefrequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use} [Only one of MnDrift, NewmanApp, or DiffQTF can be nonzero]
0 SumQTF  Full summation frequency 2ndorder forces computed with full QTF {0: None; [10, 11, or 12]: WAMIT file to use}
 FLOATING PLATFORM FORCE FLAGS  [unused with WaveMod=6]
True PtfmSgF  Platform horizontal surge translation force (flag) or DEFAULT
True PtfmSwF  Platform horizontal sway translation force (flag) or DEFAULT
True PtfmHvF  Platform vertical heave translation force (flag) or DEFAULT
True PtfmRF  Platform roll tilt rotation force (flag) or DEFAULT
True PtfmPF  Platform pitch tilt rotation force (flag) or DEFAULT
True PtfmYF  Platform yaw rotation force (flag) or DEFAULT
 PLATFORM ADDITIONAL STIFFNESS AND DAMPING 
0 0 0 0 0 0 AddF0  Additional preload (N, Nm)
0 0 0 0 0 0 AddCLin  Additional linear stiffness (N/m, N/rad, Nm/m, Nm/rad)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBLin  Additional linear damping(N/(m/s), N/(rad/s), Nm/(m/s), Nm/(rad/s))
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 AddBQuad  Additional quadratic drag(N/(m/s)^2, N/(rad/s)^2, Nm(m/s)^2, Nm/(rad/s)^2)
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
 AXIAL COEFFICIENTS 
1 NAxCoef  Number of axial coefficients ()
AxCoefID AxCd AxCa AxCp
() () () ()
1 0.00 0.00 1.00
 MEMBER JOINTS 
2 NJoints  Number of joints () [must be exactly 0 or at least 2]
JointID Jointxi Jointyi Jointzi JointAxID JointOvrlp [JointOvrlp= 0: do nothing at joint, 1: eliminate overlaps by calculating super member]
() (m) (m) (m) () (switch)
1 0.00000 0.00000 4.00000 1 0
2 0.00000 0.00000 0.00000 1 0
 MEMBER CROSSSECTION PROPERTIES 
1 NPropSets  Number of member property sets ()
PropSetID PropD PropThck
() (m) (m)
1 45.13520 0.00010
 SIMPLE HYDRODYNAMIC COEFFICIENTS (model 1) 
SimplCd SimplCdMG SimplCa SimplCaMG SimplCp SimplCpMG SimplAxCa SimplAxCaMG SimplAxCp SimplAxCpMG
() () () () () () () () () ()
1.00 1.00 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00
 DEPTHBASED HYDRODYNAMIC COEFFICIENTS (model 2) 
0 NCoefDpth  Number of depthdependent coefficients ()
Dpth DpthCd DpthCdMG DpthCa DpthCaMG DpthCp DpthCpMG DpthAxCa DpthAxCaMG DpthAxCp DpthAxCpMG
(m) () () () () () () () () () ()
 MEMBERBASED HYDRODYNAMIC COEFFICIENTS (model 3) 
0 NCoefMembers  Number of memberbased coefficients ()
MemberID MemberCd1 MemberCd2 MemberCdMG1 MemberCdMG2 MemberCa1 MemberCa2 MemberCaMG1 MemberCaMG2 MemberCp1 MemberCp2 MemberCpMG1 MemberCpMG2 MemberAxCa1 MemberAxCa2 MemberAxCaMG1 MemberAxCaMG2 MemberAxCp1 MemberAxCp2 MemberAxCpMG1 MemberAxCpMG2
() () () () () () () () () () () () () () () () () () () () ()
 MEMBERS 
1 NMembers  Number of members ()
MemberID MJointID1 MJointID2 MPropSetID1 MPropSetID2 MDivSize MCoefMod PropPot [MCoefMod=1: use simple coeff table, 2: use depthbased coeff table, 3: use memberbased coeff table] [ PropPot/=0 if member is modeled with potentialflow theory]
() () () () () (m) (switch) (flag)
1 1 2 1 1 0.5000 1 TRUE
 FILLED MEMBERS 
0 NFillGroups  Number of filled member groups () [If FillDens = DEFAULT, then FillDens = WtrDens; FillFSLoc is related to MSL2SWL]
FillNumM FillMList FillFSLoc FillDens
() () (m) (kg/m^3)
 MARINE GROWTH 
0 NMGDepths  Number of marinegrowth depths specified ()
MGDpth MGThck MGDens
(m) (m) (kg/m^3)
 MEMBER OUTPUT LIST 
0 NMOutputs  Number of member outputs () [must be < 10]
MemberID NOutLoc NodeLocs [NOutLoc < 10; node locations are normalized distance from the start of the member, and must be >=0 and <= 1] [unused if NMOutputs=0]
() () ()
 JOINT OUTPUT LIST 
0 NJOutputs  Number of joint outputs [Must be < 10]
0 JOutLst  List of JointIDs which are to be output ()[unused if NJOutputs=0]
 OUTPUT 
True HDSum  Output a summary file [flag]
False OutAll  Output all userspecified member and joint loads (only at each member end, not interior locations) [flag]
2 OutSwtch  Output requested channels to: [1=Hydrodyn.out, 2=GlueCode.out, 3=both files]
"ES11.4e2" OutFmt  Output format for numerical results (quoted string) [not checked for validity!]
"A11" OutSFmt  Output format for header strings (quoted string) [not checked for validity!]
 OUTPUT CHANNELS 
"Wave1Elev"  Wave elevation at the platform reference point ( 0, 0)
END of output channels and end of file. (the word "END" must appear in the first 3 columns of this line)

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Josh,
Well, the only real difference between these two models that I see from my quick skim is the inclusion of transverse viscous drag on the 4m long, 45m diameter striptheory member in the second model. This will add some damping not included in your potentialflowonly solution in the first model. Perhaps this small amount of damping is eliminating the instability.
Please note that I see WaveMod=0 (still water) in the first model and =1 (regular waves) in the second model, but I assume that change is not related to the differences you say were causing the instability.
Best regards,
Well, the only real difference between these two models that I see from my quick skim is the inclusion of transverse viscous drag on the 4m long, 45m diameter striptheory member in the second model. This will add some damping not included in your potentialflowonly solution in the first model. Perhaps this small amount of damping is eliminating the instability.
Please note that I see WaveMod=0 (still water) in the first model and =1 (regular waves) in the second model, but I assume that change is not related to the differences you say were causing the instability.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

 Posts: 11
 Joined: Wed Jun 03, 2020 9:23 am
 Organization: Liverpool John Moores University
 Location: UK
Re: hydrodynamic analysis of multi body platform
Dear Jason,
I have pinpointed the instability to the RdtnMod. You can see in the first Hydrodyn input file that both ExctnMod and RdtnMod = 1 where as in the second one they both = 0. I ran two more simulations the first with ExctMod =1 and RdntMod = 0 and ExctMod=RdntMod=1. Only the first simulation with ExctMod = 1 and RdntMod = 0 could finish. The second simulation observed the same instability.
Therefore, without the radiation memoryeffect model the simulations can run. This is where my knowledge of hydrodynamics falls short. Do you know why this is?
Kind regards,
Josh
I have pinpointed the instability to the RdtnMod. You can see in the first Hydrodyn input file that both ExctnMod and RdtnMod = 1 where as in the second one they both = 0. I ran two more simulations the first with ExctMod =1 and RdntMod = 0 and ExctMod=RdntMod=1. Only the first simulation with ExctMod = 1 and RdntMod = 0 could finish. The second simulation observed the same instability.
Therefore, without the radiation memoryeffect model the simulations can run. This is where my knowledge of hydrodynamics falls short. Do you know why this is?
Kind regards,
Josh

 Posts: 5778
 Joined: Thu Nov 03, 2005 4:38 pm
 Location: Boulder, CO
 Contact:
Re: hydrodynamic analysis of multi body platform
Dear Josh,
RdtnMod controls how the waveradiation "memory effect" (damping) in the potentialflow solution of HydroDyn is accounted for. RdtnMod = 0 disables the memory effect altogether; RdtnMod = 1 makes use of numerical convolution.
Normally I would expect RdtnMod = 1 to add damping to the system, but if it is causing instability, this could be tied to the WAMIT data (through the damping matrix, B, stored in the *.1 file) you are using. Is the data in the B matrix smooth, does it start at zero at zero frequency, are you computing the data to high frequency (say 5 rad/s), and does the data converge to zero at infinite frequency?
The B matrix is converted to a waveradiation kernel via a cosine transform that is used in the convolution within HydroDyn; I'm curious if this is smooth as wellit should oscillate but converge to zero as time increases. In our recent upgrades to the HydroDyn module from https://github.com/OpenFAST/openfast/pull/537 (now merged into the dev branch of OpenFAST, but not yet the main branch), the waveradiation kernel is now written to the HydroDyn summary file; before this version, the kernel could be accessed from the source code, but is not written to a file.
Best regards,
RdtnMod controls how the waveradiation "memory effect" (damping) in the potentialflow solution of HydroDyn is accounted for. RdtnMod = 0 disables the memory effect altogether; RdtnMod = 1 makes use of numerical convolution.
Normally I would expect RdtnMod = 1 to add damping to the system, but if it is causing instability, this could be tied to the WAMIT data (through the damping matrix, B, stored in the *.1 file) you are using. Is the data in the B matrix smooth, does it start at zero at zero frequency, are you computing the data to high frequency (say 5 rad/s), and does the data converge to zero at infinite frequency?
The B matrix is converted to a waveradiation kernel via a cosine transform that is used in the convolution within HydroDyn; I'm curious if this is smooth as wellit should oscillate but converge to zero as time increases. In our recent upgrades to the HydroDyn module from https://github.com/OpenFAST/openfast/pull/537 (now merged into the dev branch of OpenFAST, but not yet the main branch), the waveradiation kernel is now written to the HydroDyn summary file; before this version, the kernel could be accessed from the source code, but is not written to a file.
Best regards,
Jason Jonkman, Ph.D.
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
Senior Engineer  National Wind Technology Center (NWTC)
National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway  Golden, CO 80401
+1 (303) 384 – 7026  Fax: +1 (303) 384 – 6901
nwtc.nrel.gov
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